In use, two such supporting stays are normally provided at opposite sides of a window, the track of each stay being mounted on the window frame and the bar being mounted on the window sash. The arrangement is such that as the window pivots on the stays, about either a vertical or a horizontal axis, the axis of pivoting of the window sash moves away from the window frame so that when the window is open both sides thereof are accessible from one side of the window frame.
The window sash is frictionally restrained in any angular position to which it is set. This frictional restraint may be provided partly by the friction at the pivotal connections between the various elements but is largely provided by the frictional engagement between the slider and the track.
In friction supporting stays of this kind, the end of the track remote from the strut is normally provided with a cap member having one or more internal surfaces engageable by the end of the bar. The cap member may, for example, provide two internal cam surfaces meeting at an apex, and the end of the bar which overlies the track when the stay is in the closed position is provided with a correspondingly shaped nose portion which enters the cap member and engages the cam surfaces with a wedging action as the stay is moved into the closed position.
In friction stays having such cap members, the cap member is conventionally formed from plastics material and is riveted or staked to the metal track. The nose portion, however, normally simply comprises a shaped end portion of the metal bar. A disadvantage of known friction stays of this kind is that with repeated use the hard metal nose portion causes wear of the plastics cap member, so that, in time, the proper wedging action between the two parts does not take place.